The Fourth Circuit panel may have been baffled by the activity/inactivity distinction, as Orin reports, but it’s really not a new idea. The distinction between activity and inactivity is not an alien concept to the law. We see this distinction where the law recognizes the difference between acts of commission and acts of omission, for instance, or where there are legal (or even constitutional) distinctions made between prohibitions or limitations on conduct, on the one hand, and mandated conduct, on the other. Furthermore, if one accepts a classical liberal conception of individual liberty, the former are a qualitatively lesser infringement upon liberty than the latter. This does not, by itself, establish that the activity/inactivity distinction should be recognized as a limitation on federal power under the Interstate Commerce and Necessary & Proper Clauses. Nor does it suggest that it is always easy to draw the line separating activity from inactivity, as there may be closes cases here (as elsewhere). It does, however, suggest that there should be a bit less bafflement about the underlying concept.
An obvious example where the law has long recognized a distinction between activity and inactivity is the duty to rescue. Under the common law, simple inactivity — a failure to rescue, by itself — can never be a source of liability. Rather, the duty to rescue only arises when one engages in certain activities — that is, when one takes certain affirmative steps, such as by creating an ultrahazardous situation entering a certain type of relationship with the individual in need of rescue becoming a common carrier, or taking initial steps toward rescue. And only after certain activities are engaged in can there be liability. Whether certain activities are, or should be, the source of a duty breach of which could result in liability has prompted significant debate, but the fact that the common law required activity of some sort before a duty could arise is clear. In other words, under the common law, activity could create the duty but inactivity could not.
We can also see analogous distinctions made in some areas of constitutional law. Under current First Amendment doctrine, for example, the government’s ability to compel speech is greater once a speaker engages in a relevant activity than when a would-be speaker has done or said nothing. So, for instance, the government can mandate that those engaged in dangerous activities post warnings or that potentially misleading speech be cured by disclaimers. But the government lacks any general ability to simply mandate speech across the board. Again, the law recognizes that engaging in certain sorts of activity may result in legal obligations where simple inactivity, doing nothing, does not.
One way to think about the activity/inactivity distinction is to recognize the difference between prohibiting conduct or imposing conditions on conduct, on the one hand, and mandating conduct on the other. We see this distinction in the Supreme Court’s current federalism jurisprudence. The federal government may prohibit (preempt) states from engaging in certain activities under the Supremacy Clause. It may also subject states to generally applicable regulations if states engage in those activities that would make them subject to such rules, e.g. if states become market participants, employers, property managers, etc. The federal government may not, however, simply commandeer states to engage in activities because that is what the federal government wants. That is, once states engage in certain activities, the federal government may be able to regulate how those activities are conducted, but it may not mandate that states engage in certain activities in the first place. Even under the 14th Amendment, we see plenty of areas in which Congress may require states to administer state-run programs in a particular way, so as to ensure equal protection or prevent the infringement of fundamental liberties, but few if any in which “inactive” states are mandated to do something in the first place.
As noted above, the idea that there is a fundamental difference between a prohibition or conditional regulation, on the one hand, and a mandate, on the other, follows from a classical liberal conception of individual liberty. From this perspective, a naked mandate — a requirement that one engage in an activity — is a greater imposition than a prohibition or a conditional regulation. Why? Think of it this way. At any given moment, an free individual can engage in a near-infinite set of activities (n). A government prohibition reduces this set by one (to n-1). A conditional regulation has a similar effect, in that it imposes a burden on one activity, but it does not otherwise reduce the set of options. A mandate, on the other hand, requires that at a given moment the mandated individual engage in the required activity, to the exclusion of all else. If a person were mandated to wash his car, that time cannot be spent doing other things. The loss of opportunities is near infinite — indeed, it is n-1 — insofar as the mandate precludes the individual from doing other things simultaneously. Therefore, a simple prohibition or conditional regulation is a rather minor limitation on individual liberty, whereas a mandate is not.
The same logic applies to economic mandates. A free person can spend a dollar on a nearly-infinite set of things. A prohibition on the purchase of a good or service reduces the set by one. You may not be able to buy X, but you still have a near-infinite set of options for how to use the dollar. A conditional regulation — if you buy X, you must also buy Y or may only buy X if it meets certain conditions — still does not impose a categorically greater imposition. You still have a near-infinite set of alternative uses for that dollar. When the government mandates that you purchase something, be it health care, a fitness club membership, broccoli, or whatever, you lose the ability to spend that dollar on anything else. Your set of options for that dollar has been completely extinguished, and the set of opportunities has been definitively reduced. This does not mean that mandates are necessarily unconstitutional, only that they are qualitatively different in a way that helps us understand the distinction between regulating activity and mandating activity (which is just another way of saying “regulating inactivity”).
[A quick note on taxes. Taxes have the same effect as a mandate. This is why taxes are viewed with such hostility and suspicion, even if they are necessary. It is no accident that, in McCulloch v. Maryland, Chief Justice Marshall called the power the tax the "power to destroy," or that the founders felt the need to separately enumerate, and constrain, the taxing power.]
To be clear, my argument in this post is not that an activity-inactivity distinction is self-evidently imposed by the Constitution (though I believe such a distinction is consistent with current precedent and ought to be adopted), or that the individual mandate should be held to be unconstitutional (though I believe that as well). My point here is simply that the activity-inactivity distinction is not some alien invention of libertarian academics, and not qualitatively different from distinctions we see in the law and our legal tradition. Whether this means the distinction should be incorporated into (or made explicit within) existing enumerated powers doctrine is a separate question for another time.